In the world of amateur radio, making contacts with operators across the globe has always been a thrilling experience. One particularly exciting way to achieve this is through **satellite communication**. Today, BD7LLY will introduce what satellites are, how they relate to amateur radio, the different types of satellites, how they move, and what you need to get started in satellite communication.
1. What Are Satellites? What’s Their Connection to Amateur Radio?
Satellites are objects that orbit the Earth (or other celestial bodies). In communication, satellites act as relays, receiving signals from one point on Earth and retransmitting them to another. **Amateur radio satellites**, specifically designed for ham operators, provide the means to establish long-distance communications by sending signals up to space and back down to distant locations.
These satellites are commonly referred to as OSCARs (Orbiting Satellites Carrying Amateur Radio). They are launched by various amateur radio organizations, universities, or private entities with the primary purpose of supporting communication, education, and scientific experimentation. With the help of these satellites, amateur operators can make contacts across continents, sometimes even halfway around the world!
2. Types of Satellites: Which Ones Can Be Used for Amateur Radio?
In amateur radio, there are two main types of satellites that operators can work with:
1. Low Earth Orbit Satellites (LEO)
– These satellites orbit the Earth at altitudes of about 300 to 1,500 km and complete one orbit in roughly 90 minutes. Popular satellites like AO-91 and SO-50 fall under this category. Since they move quickly, each pass over a specific location only lasts around 10-15 minutes.
2. Geostationary Orbit Satellites (GEO)
– These satellites orbit much higher, at about 36,000 km above the equator, and appear stationary relative to the Earth’s surface. The most well-known amateur geostationary satellite is QO-100 (Es’hail-2), which provides continuous coverage over **Europe**, **Africa**, and parts of **Asia**. However, it is not accessible in most parts of China, except for a few regions in the far west.
Additionally, there are small CubeSats (miniature satellites) often launched by universities for scientific purposes, some of which carry amateur radio transponders. Examples include AO-109 and **PO-101**.
3. How Do Satellites Move? When Can We Use Them?
The movement of a satellite and its orbit determine when and how we can communicate via them.
– **LEO Satellites**: These satellites move quickly, orbiting the Earth in about 90 minutes. They pass over a specific location multiple times a day, but the window of time when they are usable is brief—usually 10 to 15 minutes per pass. To know exactly when a LEO satellite will be overhead, you need satellite tracking software (such as Heavens-Above or **GPredict**) to predict when and where it will pass over your location.
– **GEO Satellites**: A geostationary satellite like QO-100 stays fixed over a specific region of the Earth, offering continuous coverage as long as you are within its footprint. Since it doesn’t move relative to the Earth, you can use it at any time, provided you are in the coverage area.
4. What Equipment Do You Need to Communicate via Satellites?
To communicate through satellites, you’ll need the following equipment:
1. **Dual-Band Handheld Transceiver (HT)**: Most amateur radio satellites use VHF (2 meters) for uplink and UHF (70 cm) for downlink (or vice versa). Radios like the **Icom IC-705**, **Yaesu FT-817ND**, or even entry-level ones like the Baofeng are capable of working these satellites.
2. **Directional Antenna**: Since satellites are moving targets, you need an antenna that can accurately point toward them. The most common choice is a **Yagi antenna**, which is lightweight and easy to manually aim at a satellite as it passes overhead.
3. **Satellite Tracking Software**: Tools like **Heavens-Above**, **GPredict**, or ISS Detector help you track satellite orbits and tell you when a satellite is in range for communication. These tools also provide essential information such as the satellite’s azimuth (direction) and elevation (how high it will appear in the sky).
4. **Frequency Adjustment for Doppler Shift**: As a satellite moves closer to or farther from you, the frequency of its signal shifts due to the **Doppler effect**. You will need to adjust the frequency of your radio during a satellite pass to compensate for this. Many tracking tools can help you calculate and adjust for Doppler shift.
5. **Logging QSOs**: When making contacts via satellite, it’s important to log your QSOs (contacts). This can be done using QSL cards or an electronic log to record the contact details.
Conclusion
Communicating via amateur radio satellites is a fun and challenging way to connect with operators around the world. By understanding satellite movements, preparing the right equipment, and using tracking tools, you can successfully make satellite QSOs. As technology advances, more and more amateur satellites will be launched, offering even greater opportunities for hams to explore space-based communication.
BD7LLY looks forward to catching you on the air—via satellite!